Projection & Display Systems
Introduction
Everything else in a video system exists to get a picture onto the screen the audience is looking at. The best camera work, the cleanest signal and the sharpest graphics are lost if that screen is too dim for the room, too small for the back row, warped by keystone, blotchy with mismatched LED panels, or hung where heads block half of it.
This book is about that last stage: projectors and screens, LED walls and flat panels, how to choose between them for a room, how big and how bright they must be, and how to set them up so the picture is as good as the signal feeding it.
It draws on published sources: AVIXA's standards for image size and projected contrast, and the documentation of projector, screen, LED and display makers. Where it gives a number, it says where the number comes from, and where it works one out, it shows the working.
How to Use This Book
Read it in order: projection, then LED, then flat panels, then choosing and setting up. Video Intermediate covers the signal that reaches each display, and Display and Confidence Monitoring covers the screens that face the stage rather than the audience.
Sit in the worst seat
Every judgement in this book is made from the audience's side, and most of all from the worst seats: the back row, the far side, the seat behind the tallest head. Before any show, sit there and look.
Display Systems
Where the video image reaches the audience.
The last stage
Display systems are the last stage of the video chain — where the image, after being captured, processed, switched, and routed, is finally shown to the audience. A display (a projector and screen, an LED wall, or a flat-panel screen) takes the video signal and turns it into the image people see. No matter how good the rest of the video chain, the display is what the audience actually experiences — so getting the display right is essential. The display is where the image reaches the audience.
This matters because the display determines what the audience sees — its size, brightness, sharpness, and quality directly shape the experience. A great display well set up makes the content look great; a poor or badly set-up display undermines it. Display work — choosing and setting up the right display well — is essential to video. The display is the audience's view of all the video work.
Display technologies
There are three main display technologies. Projection — a projector throws the image onto a screen or surface (flexible, can be very large, but needs darkness/brightness management and a surface). LED walls — direct-view LED panels assembled into a screen that emits the image directly (bright, vivid, scalable, increasingly common for big screens and stages). Flat-panel displays — screens/monitors (TVs, professional displays — sharp and bright, but size-limited, good for smaller applications and signage). Each technology has its strengths and uses. Understanding the display technologies is fundamental to display work. Projection, LED, and flat-panels are the main ways to show the image.
Each suits different situations (projection for large images in controllable light, LED for bright big screens and stages, flat-panels for smaller/sharper applications), and display work involves choosing and using the right one. Understanding the technologies — what each is and where it's used — is the basis for display work. The professional knows the display technologies and their uses.
Practice it
Three rooms need screens: a 30-seat breakout room with daylight, a dimmable 500-seat ballroom, and an outdoor festival stage.
Projection
Projectors, brightness, throw, and screens.
Projector basics
Projection uses a projector to throw an image onto a screen or surface. Key projection concepts: brightness (measured in lumens — the projector must be bright enough to overcome the ambient light in the room; more ambient light needs more lumens). Throw (the distance from projector to screen, and the lens, which together determine the image size — throw ratio relates distance to image width). Resolution (the projector's pixel detail). And the screen/surface (the surface the image is projected onto, which affects brightness and quality). Understanding these is fundamental to projection. A projector's brightness, throw, and screen determine the image.
Getting projection right means matching the projector (brightness, throw/lens, resolution) to the venue (size, throw distance, ambient light) and the screen, so the image is big enough, bright enough, and sharp. A common projection failure is too little brightness for the ambient light (a washed-out image). Understanding projector basics is essential to projection. The projector must be matched to the venue and screen for a good image.
Setting up projection
Setting up projection well means placing the projector (the right distance and position for the image size and a square, aligned image), choosing/setting the lens for the throw and size, getting the image onto the screen correctly (aligned, the right size, square — not keystoned/distorted), focusing it sharp, and optimising the image (brightness, colour). For multiple projectors (blending several into one large image — common for very wide projection), the images must be aligned and blended seamlessly. Setting up projection correctly delivers a big, bright, sharp, aligned image. Understanding projection setup is central to projection work. The professional sets up projection for a great image.
Good projection setup makes the image look great (correctly sized, square, sharp, bright); poor setup gives a distorted, soft, or washed-out image. The professional sets the projector and screen up carefully and optimises the result. The professional delivers a well-set-up projected image.
Brightness, and why the room decides
A projector's brightness is given in lumens, measured, as Texas Instruments' design note explains, by averaging the light at nine points across a full white image. That is a property of the projector alone. What the audience sees is the brightness of the screen, in nits, candelas per square metre, and that depends on how big the picture is and how the screen reflects.
TI gives the relationship for a plain matte screen: nits equal lumens times screen gain, divided by pi times the screen's area in square metres. A 4-metre-wide 16:9 screen is 2.25 metres high, 9 square metres. A 10,000-lumen projector on a matte screen of gain 1 gives about 10,000 divided by 28, roughly 350 nits. Double the screen's width and the area is four times larger, so the same screen brightness needs four times the lumens.
How much is enough depends on the room. TI's table of suggested minimums runs from 50 nits in a dark room and 100 in a dim one, to 200 in a well-lit room with no daylight, 300 to 400 with windows and indirect daylight, and 600 or more outdoors in indirect sun. For comparison, SMPTE sets the cinema standard at 48 nits, 14 foot-lamberts, in a room that is completely dark.
The reason is contrast. A projector cannot make black; black on a screen is simply the room's own light falling on it. Take that 350-nit picture into a room where the house lights put 25 nits of light on the screen. White is now 350 plus 25, and black is 25, so the contrast is about 375 divided by 25, 15 to 1. Turn the room lights down so only 5 nits fall on the screen and the contrast climbs to about 70 to 1. The projector has not changed; the room has.
AVIXA's standard for image system contrast sets minimums by what the audience must do: its pages give 15 to 1 for basic decision making, such as reading a presentation, and 50 to 1 for analytical work. Dataton's summary of the same standard adds 7 to 1 for passive viewing and 80 to 1 for full-motion video. Gerriets, a screen maker, puts it in plainer words for conference rooms: 6 to 1 to 10 to 1 looks bad, 20 to 1 and up looks good.
Throw ratio and lenses
The throw ratio is the distance from the lens to the screen divided by the width of the picture. Barco's lens lexicon gives the plain example: a 2.0 to 1 lens must be twice as far from the screen as the screen is wide. A 4-metre-wide screen with that lens needs the projector 8 metres back.
Venue projectors take interchangeable lenses, from ultra-short throws that sit almost at the screen to long throws that reach from the back of a hall. Panasonic's ET-D75LE95, for example, has a throw ratio of about 0.36 to 1, so the same 4-metre screen could be filled from about 1.4 metres away. Barco notes that the ratio also depends on the size of the projector's imaging chip, so the same lens gives a different ratio on a different projector. Always read the ratio from the table for the exact projector and lens.
Throw ratio, screen size and brightness are linked. TI points out that at a fixed distance a shorter throw makes a bigger picture, which is a dimmer one.
Lens shift and keystone
A projector rarely sits square in front of the middle of its screen. It hangs above it, or sits low, or off to the side. There are two ways to put the picture on the screen anyway, and they are not equal.
Lens shift moves the picture optically, by moving the lens across the face of the imaging chip. The picture stays a perfect rectangle at full resolution. Barco quotes up to 130 per cent vertical and 50 per cent horizontal shift on some of its projectors and lenses, and notes that makers measure shift differently, some from the lens's centre line and some from the screen's bottom edge, so compare the definitions as well as the numbers. The range depends on the pair: Panasonic's ET-D75LE95 shifts differently on each projector it fits.
Keystone correction squeezes the picture digitally to undo the trapezoid of an angled projector. Barco is blunt about it: digital keystone compresses the image with a loss of resolution and noticeable artefacts at the edges. Use lens shift and placement first, and keystone only for what is left.
Screens: front, rear and gain
Screen gain compares a screen's brightness with a perfect matte white surface, which has a gain of 1. SMPTE's method measures it on the axis and at 5-degree steps to the side, and warns that the headline gain figure is misleading: a high-gain screen is only that bright at its hot spot, straight down the projector's axis.
Gerriets' measured curves show the trade. Its matte white front screen has a gain of 0.98 straight on and 0.83 at 30 degrees, so the picture looks almost the same from every seat. Its high-gain front screen reaches 1.89 straight on but only 0.70 at 30 degrees: brighter for the middle seats and dimmer at the sides than the matte screen. Its grey screen, 0.61 straight on, gives up brightness for contrast in brighter rooms. As Gerriets puts it, the higher the gain, the narrower the viewing cone. Screen makers describe that cone by the half-gain angle, the angle at which the screen's gain falls to half its value straight on; the wider it is, the more evenly the seats are served. SMPTE advises that screens above a gain of 1.3 be curved.
Front projection needs no space behind the screen, but its light surface also reflects the room's light, presenters walking in the beam cast shadows, and stage lighting demands a brighter projector. Rear projection puts the projector behind the screen. It needs space, but there are no shadows, the grey or dark screen ignores much of the room's light for better contrast, and the screen disappears when it is off.
Blending and warping
A picture wider than one projector can fill is made by edge blending: two or more projectors overlap, and each fades its picture across the overlap so the join disappears. Dataton's WATCHOUT guide suggests an overlap of 10 to 20 per cent of the projector's width and warns that below 5 per cent is hard to blend invisibly. Resolume recommends at least 15 per cent.
Black is the hard part. Projectors never project true black, so in the overlap two projectors' blacks add up and the join glows in dark scenes. Epson's manuals describe the fix, raising the black level of the areas outside the overlap to match, and VIOSO, which makes blending software, is plain that it always costs contrast. Gerriets adds that high-gain screens show darker, uneven areas at the overlap; matte screens blend best.
Warping reshapes a projected picture to fit a curved screen or an odd shape, and projection mapping takes it further, fitting pictures to a building, a set or an object. Both are done in the projector's own geometry tools or in a media server, and both start from the same care as a single screen: brightness, throw and lens shift first, correction last.
Practice it
A conference room has a 4-metre-wide 16:9 screen, matte white, gain 1, with daylight through windows down one side.
- You can turn lumens into nits for a given screen.
- You check the room's light before choosing brightness.
- You can work out throw distance from a throw ratio.
- You use lens shift before keystone.
- You choose screen gain knowing what it costs the side seats.
- You know why blends show in dark scenes and what fixes cost.
LED & Flat-Panel Displays
Direct-view LED and screens.
LED walls
LED walls (direct-view LED) are screens built from LED panels (tiles) assembled into a large display that emits the image directly — increasingly common for big screens, stages, and high-brightness needs. Key LED concepts: pixel pitch (the spacing between LEDs — smaller pitch means finer resolution and closer viewing; larger pitch is for bigger/farther screens), brightness (LED is very bright, working even in bright environments), and assembly (panels are rigged/stacked into the screen, then driven by a processor that maps the video onto the panels). LED walls are bright, vivid, scalable, and seamless. Understanding LED walls is central to modern display work. LED walls are bright, scalable direct-view screens.
LED is now dominant for many big-screen applications (concerts, events, broadcast backdrops, large signage) because it's bright (works in any light), scalable (build any size from panels), and impactful. Setting up LED involves assembling/rigging the panels and configuring the processor to drive them correctly. LED walls are a major, growing display technology.
An LED wall is built from cabinets, each covered in modules of LEDs, locked together into one surface. Each cabinet carries its share of the picture as data from the processor, passed from one cabinet to the next, and its own power. ROE's Black Pearl BP2, an indoor panel common at events, is 500 millimetres square with 176 by 176 pixels at a 2.84-millimetre pitch, calibrated to a maximum of 1,500 nits, with a 140-degree viewing angle. ROE's Carbon5L, an outdoor panel, reaches 5,000 nits, weatherproofed to IP65.
Modules fail one at a time, and a single dark square in a bright wall is obvious. Carry spare modules from the same batch, and know how to swap one quickly. ROE's modules store their own calibration data, so it travels with the module.
Flat-panel displays
Flat-panel displays (screens/monitors — LCD, OLED, and similar) are self-contained displays used widely in AV: professional displays and TVs for presentations, signage, monitoring, and smaller-audience viewing. They're sharp, bright, reliable, and simple (a screen you feed a signal to), but size-limited (though large panels and video walls of tiled panels exist). Flat-panels are the go-to for many applications (meeting rooms, signage, monitors, smaller venues) where a projector or LED wall isn't needed. Understanding flat-panel displays completes the display picture. Flat-panels are sharp, simple displays for many applications.
Flat-panels are everywhere in AV (the displays in meeting rooms, the screens of digital signage, monitors), and display work includes selecting, mounting, and feeding them correctly. They're the simplest display type but still must be chosen (size, type) and set up well. Flat-panel displays serve the many applications that need a screen.
Flat panels are the right choice where the audience is small and close: breakout rooms, lobbies, side screens. Commercial panels are built for long hours that consumer televisions are not; Samsung's VMC-R video wall panel, for example, is rated for 24-hour, 7-day operation at a typical maximum of 500 nits.
Panels tile into video walls. The seam is the cost: even on thin bezel panels such as the VMC-R, under a millimetre wide, a line crosses the picture between every panel, which matters for text and faces and matters little for abstract graphics.
Pixel pitch and viewing distance
Pixel pitch is the distance between the centres of neighbouring pixels, in millimetres. Planar gives two ways to turn it into a viewing distance. The precise one is visual acuity: multiply the pitch in millimetres by 3,438, the factor for one minute of arc, to get the distance in millimetres at which a viewer with normal sight stops seeing individual pixels. The quick one is the ten-times rule: the pitch times ten gives the same acuity distance, roughly, in feet, so a 2.5-millimetre pitch gives 25 feet, about 7.6 metres.
Planar's own chart shows the result. A 1-millimetre pitch reaches its acuity distance at about 3.4 metres, a 2.5-millimetre pitch at about 8.6 metres, and a 10-millimetre pitch at about 34 metres. It also gives an average comfortable viewing distance at roughly half the acuity distance, so a 2.5-millimetre wall is comfortable from about 4.3 metres back.
The two distances measure different things, so use each for its own job. The acuity distance is where the picture becomes seamless: use it when the closest seats must read small text, spreadsheets or fine detail, or when the client wants a wall with no visible pixels. The comfortable distance is where most people find the picture acceptable, based on Planar's real installations: use it as the minimum for the front row when the content is video and large graphics. Between the two, viewers can see the pixel grid if they look for it, but the picture still works.
So choose pitch from the closest seat, not the furthest. A coarse pitch is fine and far cheaper for a festival stage seen from 30 metres; the same pitch looks like a grid of dots to the front row of a ballroom.
LED processors and scaling
The processor sits between the video system and the wall. It takes the signal in, scales it, corrects colour, and maps each part of the picture to the right cabinet, pixel for pixel. Its outputs feed the receiving cards in the cabinets over network cable.
Every processor output carries a limited number of pixels. Brompton lists its Tessera S4 at about 2.1 million pixels across four 1G ports, with two frames of latency, and its SX40 at about 9 million across four 10-gigabit ports, each breaking out to as many as ten 1G connections. Work out the wall before booking the processor. A wall of BP2 panels 12 wide and 6 high is 2,112 by 1,056 pixels, about 2.2 million: just over an S4's nominal capacity, and well within an SX40's.
Colour, brightness and calibration
LEDs vary. Two batches of the same panel, made months apart, can differ slightly in colour and brightness, and side by side the wall looks like a patchwork. Calibration measures each LED and corrects it to a common target. Brompton has described the price of the usual method: every LED is brought down to match the dimmest and palest in the wall, so uniformity costs brightness and colour range.
The working rules follow. Build a wall from one batch where possible, keep spares from the same batch, recalibrate when panels are mixed, and run the wall at the brightness the room needs, not the most it can do. A wall at full brightness in a dark ballroom is uncomfortable to look at and overwhelms the faces on camera in front of it.
On camera: moiré and scan lines
An LED wall in front of a camera brings two problems. The first is moiré, the rippling bands that appear when the grid of the wall's pixels meets the grid of the camera's sensor. Panasonic explains that the black gaps between LEDs effectively double the frequency of the pattern, and lists the cures: shallow focus so the wall is soft, the subject as far from the wall as possible, the iris open with ND to hold exposure, the camera further back on a longer lens, and the finest pitch you can afford. Moiré is optical, so electronic processing in the camera does little.
The second is flicker and scan bands, dark lines rolling through the wall on camera. They come from the way LED drivers switch the pixels. ROE notes that high refresh rates avoid visible scan lines, and its BP2 refreshes at 7,680 hertz. Planar explains that a lower scan ratio, fewer lines per driver chip, leaves more time to refresh. On the processor side, Brompton's ShutterSync adjusts the wall's refresh timing to suit the camera's shutter and works with genlock.
Practice it
A ballroom's front row is 4 metres from the stage, where a 6 by 3 metre LED wall will stand, and the show will be filmed.
- You choose pitch from the closest seat.
- You count the wall's pixels against the processor's capacity.
- You keep panels and spares from one batch, and recalibrate when mixing.
- You run the wall at the brightness the room needs.
- You know the camera cures for moiré and scan lines.
Choosing & Optimizing
Pick the right display and make it look great.
Choosing the right display
A key skill is choosing the right display for the situation — matching the technology to the venue, audience, content, and conditions. Considerations: the size needed (how big must the image be for the audience), the brightness needed (the ambient light — bright rooms favour LED or very bright projectors/panels; dark rooms allow projection), the viewing distance (affects resolution/pixel pitch needed), the budget, and the application. Choosing well (projection vs. LED vs. flat-panel, and the specs) gets the right display for the job. Understanding how to choose the display is central to display work. The professional chooses the right display for the venue and content.
Choosing the wrong display (too dim for the room, too small for the audience, wrong type for the application) gives a poor result; choosing the right one sets up success. The professional weighs the factors and selects the appropriate display and specs. The professional matches the display to the need.
Start from the furthest seat. AVIXA's DISCAS standard sizes a screen so the smallest important element, a letter on a slide, can be read from the back row. For material people read, its figure is that the furthest viewer can be at most 200 times the element's height away. A back row at 15 metres needs letters at least 75 millimetres tall. If the slides' smallest text is 3 per cent of the screen's height, the screen must be at least 2.5 metres high, about 4.4 metres wide at 16:9. For analytical material, such as engineering drawings, DISCAS's factor is 3,438 instead, tied to the eye's ability to see one line pair.
Epson's rule of thumb gives the same answer for that room: the furthest viewer at up to six times the screen height for presentations, four for detailed material, and eight for video. Fifteen metres divided by six is 2.5 metres.
Then check the front row and the sides. Gerriets gives the DIN guideline that nobody should sit closer than one and a half times the screen's width. And check sightlines from the back: the bottom of the picture must clear the heads in front. AVIXA's calculator suggests 1.2 metres as a seated eye height, 1.5 metres standing, when nothing better is known.
| Choice | Best where | Watch for |
|---|---|---|
| Projection | Large pictures on a budget, dimmable rooms, blends and mapping | Room light, throw distance, shadows |
| LED wall | Bright rooms, stages, outdoors, any size | Pitch against closest seat, cost, moiré on camera |
| Flat panels | Small rooms and close audiences | Seams in video walls, size limits |
Setting up and optimizing the image
Whatever the display, setting it up and optimising the image makes it look its best: placing/rigging it correctly, feeding it the right signal (correct resolution/format — from Video Intermediate), and optimising the image (brightness, contrast, colour, sharpness — set correctly for the content and conditions). A well-set-up, optimised display shows the content at its best; a poorly set-up one (wrong signal, bad settings, poor placement) looks bad however good the display. The professional sets up and optimises the display so the image looks great. Setting up and optimising the image is central to display work. The professional makes the display look its best.
This applies signal knowledge (feeding the right signal correctly) and image optimisation (the display set up for a correct, great-looking image) to get the best result. Combining the technologies, projection, LED, flat-panels, choosing, and optimising is display work. The professional gets the right display, set up to show the image at its best. This is display work in action — the image reaching the audience, looking great. The display is where all the video work is finally seen.
Set up with test patterns, never with the client's content. A grid shows focus and geometry across the whole screen; colour bars and ramps show colour and banding; full white and full black show uniformity and blends. Fix in this order: placement and lens shift, then focus, then geometry, then colour, then brightness.
Flat panels hide one trap. Most crop the edges of a video signal by default, a habit from broadcast television; LG's documentation puts it at 1 to 2 per cent, and calls the setting that stops it Just Scan. Other makers use other names. With it left on, the edges of every slide are cut off and the picture is slightly scaled, and soft. Turn it off on every panel.
Measure what matters. A colour meter on the screen confirms brightness in nits against the target for the room, and colour against the system's white point. On a large show, matching every screen's white and brightness to each other is as important as each one being right.
Practice it
A conference for 400 people has its back row 18 metres from the screen, and slides whose smallest text is about 3 per cent of the screen height.
- You size from the back row with DISCAS or the six-times rule.
- You check the front row distance and the sightlines.
- You choose between projection, LED and panels for the room.
- You set up with test patterns in a fixed order.
- You turn off overscan on every flat panel.
Mastering Display Systems
The craft of getting the image seen, well.
The display professional
Pulling it together, projection and display systems is getting the video image seen — understanding the technologies (projection, LED, flat-panel), choosing the right display for the venue and content, and setting it up and optimising the image to look its best. The display professional combines display-technology knowledge, projection and LED expertise, selection judgement, and setup/optimisation skill. This makes them able to deliver the image to the audience at its best — the crucial last stage of the video chain — and it is a valuable video skill across events, venues, integration, and broadcast. Display systems mastered is getting the image seen, looking great, wherever it's shown.
Display work is essential and everywhere (every video application ends in a display), and as displays grow (huge LED walls, complex projection, video walls), display expertise is increasingly valuable. Understanding projection and display systems — the technologies, selection, and setup — is a valuable, practical video capability. The display professional delivers the image to the audience, at its best.
Developing display expertise
Developing display expertise means learning the technologies deeply (projection, LED, flat-panel — their specs and setup), getting hands-on setting up real displays (projectors, LED walls, displays), learning to choose and optimise displays, and building experience across applications (events, venues, integration). It connects to Video Intermediate, LED video/creative, and integration. The best display professionals know the technologies thoroughly, choose and set up displays expertly, and optimise images beautifully, built through hands-on work. Deliberately developing these is the path forward.
From here, growing means working with bigger and more complex display systems (large LED, multi-projector blends, complex video walls), specialising (LED, projection, integration displays), and building towards senior display and video roles. Display work is a practical, in-demand, growing video field. The skills this book brings together — technologies, projection, LED, flat-panel, selection, optimisation — are the foundation; mastery comes from setting up many displays well. Keep working with displays, keep building your expertise, and you grow into a display systems professional.
Practice it
You are asked to recommend a display for a hotel ballroom keynote with the house lights partly up, an audience of 600, and a live stream.
Glossary
| Brightness (lumens) | A projector's light output vs. ambient light |
| Flat-panel | A self-contained screen/monitor display |
| LED wall | A screen of direct-view LED panels |
| Pixel pitch | The spacing between LEDs (finer = higher res) |
| Projection | Throwing an image onto a screen/surface |
| Screen | The surface an image is projected onto |
| Throw | Projector-to-screen distance (sets image size) |
| Video wall | Multiple displays/panels tiled into one screen |
| Nits | Screen brightness in candelas per square metre; lumens times gain over pi times area |
| Throw ratio | Distance from lens to screen divided by picture width |
| Lens shift | Moving the picture optically, keeping full resolution |
| Keystone correction | Squeezing the picture digitally, at a cost in resolution |
| Screen gain | Brightness compared with a matte white surface of gain 1 |
| Half-gain angle | The angle at which a screen's gain falls to half its centre value |
| Edge blending | Overlapping projectors with faded edges to make one picture |
| Visual acuity distance | Pixel pitch in millimetres times 3,438, where pixels stop being visible |
| Scan ratio | How many lines of LEDs one driver chip controls; lower leaves more time to refresh |
| LED processor | The device that scales, corrects and maps video to an LED wall's cabinets |
| Calibration | Measuring and correcting LEDs or displays to a common colour and brightness |
| Moiré | Rippling bands where a camera's sensor grid meets an LED wall's pixel grid |
| Overscan | A display cropping the picture's edges; turn it off with settings such as Just Scan |
Where to Go Next
Video Intermediate covers the signal behind every display, Display and Confidence Monitoring the screens facing the stage, and Camera Theory and Camera Intermediate what a camera sees when it points at an LED wall. Visual Aesthetics for AV covers what should go on the screen.
The first ninety days
Four things. Work out the screen brightness in nits for every projected screen you set up, and compare it with the room. Check every screen from the back row and the far side seats. Learn your LED processor's test patterns and calibration. And turn off overscan on every flat panel you touch.
What the gear actually looks like
Every device named in this book, in one place. Recognition is the whole point of Chapter 4 — use this page to attach a picture to each name before you meet it on a dock at six in the morning.
Find the destination.
Work along the path between them.